The field of this invention relates to foliage removal in growing crops, specifically pruning, shoot removal, and leaf removal in vine grown crops such as grapes.
There have been numerous attempts in the past to mechanize the task of pruning grape vines. Grape vines characteristically are hand pruned. All known attempts to this point in time to mechanize pruning have involved the use of mechanical cutting means, such as oscillating sickle cutters or rotary saw blades. Most modern vineyards are trellised, which means that there are steel stakes placed in the ground next to the vine with wires stretched down the row of steel stakes. Typically, there is a stake every five to seven feet along the row and the row may be as much as a quarter of a mile long. The wires are attached from stake to adjacent stake making an array similar to a fence running in the “down the row” direction. The grape vines are trained up the stake to the wire and then cordoned up and down the wire in the direction of the row. These stakes and wires are necessary to support the grape vine and its foliage as well as the crop the vine produces. The trellising of grapes has been an important step in making the mechanical harvesting of grapes possible. The trellising is also important in making the mechanized pruning of grape vines possible.
As mentioned hereinbefore, the current styles of mechanized pruning all share the common means of “cutting” by either impact or shear. The cutting motion is created by either a reciprocating motion in the case of sickle teeth, or by a rotary motion in the case of saw blades and the like. With either of these methods of cutting, there can be a problem with the cutting device getting tangled up in the steel stakes or trellis wires. When this occurs damage can be extensive to the pruning equipment as well as to the stake array and the trellising wire. Often along such trellised rows a leaning stake or a broken wire may be encountered which enter into the path of the pruning cutters. Cutters positioned above the cordon as they move along the row must be tripped and withdrawn from the row to keep from contacting a stake. When the cutter is kicked away from the row to bypass a stake and then reinserted into the row as the cutter passes the stake there then exists a sizable length of the vine row that does not get pruned.
The mechanical cutting devices share common problems. They usually have a large number of moving parts, are expensive to maintain and often require removal of the cutting edges and re-sharpening before proceeding with the pruning operation. Mechanical cutters also have the potential of tangling with the trellising wires, and can consequently tear vines out of the row as well as causing the aforementioned extensive damage to the cutting machinery.
The cut in the vine wood needs to be clean and smooth. If the mechanical cutting device is dull, the effect is to bludgeon the wood until it breaks. The result is to shatter the cane, causing it to die back several inches from the shattered portion. This shattered cane wood also provides a home for vineyard pests and diseases. If a vineyard is infected with a spore type of disease, the disease can be carried to the next vineyard due to contamination carried by the cutting blades. Furthermore, with the high speed of the rotary type of cutters, such as the rotating saw blades and rotary lawnmower blade configurations, there is a safety concern. With these types of cutters there is always flying debris, and personnel other than the protected operator must be required to remain several hundred feet away from the machinery during operation.
There are times when just prior to full maturity of the grapes the winemakers and/or growers want to remove leaves from the fruiting area of the vine to allow sunlight to get into the fruit so as to gain additional color in the grape bunches. To remove these by hand can be expensive and time-consuming. Some of the attempts to mechanize leaf removal have been to use vacuum type devices to suck the leaves into a rotary cutter which chews them up. Another device that has been tried in the past uses high pressure blasts of air to basically shred the leaf into fragments. These attempts at leaf removal have been only partially successful at best, and have been costly to operate. Moreover, this type of equipment is “single purpose” only, thereby serving its purpose for a very short period of time during each growing season and being relegated to storage thereafter.
In high quality grape growing areas there are times when the wineries that buy the grapes from the growers request or demand that only a given amount of grapes be produced per vine. The theory is that the vine will produce a better quality grape if the vine is not loaded with as much crop as it can naturally produce. To accomplish this, the growers must go into the field and do shoot thinning. Shoot thinning is the process of cutting off a number of shoots growing out of the cordon, which in turn reduces the amount of fruit bearing wood left on the vine. Shoot thinning is normally done by hand. There have been some attempts to mechanize shoot thinning by striking the vine with nylon or fiberglass rods in a side to side motion to break off some of the shoots. This mechanical approach can be more damaging than intended to the vine. Beating the vines hard enough to break off some shoots may be damaging other shoots microscopically, and damage is difficult to predict and therefore avoid. This is not a very successful method, due to lack of control of the amount of breakage and damage to the vine.